This invention relates to a catalytic system for polymerizing olefins, a novel component of the system containing titanium halide, a process for preparing the novel component containing titanium halide, and the use of the system in polymerizing olefins, especially propylene.
The polymerization of olefins by coordinate complex catalytic systems, often termed Ziegler-Natta catalysis, has been well-known for over 25 years. Generally, there are two components in this type of system: the catalyst containing a titanium or other transition metal halide, and the cocatalyst based on an organoaluminum compound or its substitute. The cocatalyst may be accompanied by an electron donor. Although thousands of such catalytic systems have been disclosed, there is always a quest for improvement in two important properties: activity and isotatic index.
Activity is measured by the grams of polyolefin produced per gram of titanium component or other transition metal component employed in the catalytic system. The higher the activity, the lower the amount of metallic ash and corrosive halide left in the polymer. If the activity is high enough, then the de-ashing step in processing the final polyolefin can be omitted - an important improvement.
For olefins, such as propylene, which can form isotactic structures, the higher the isotactic index, the better the physical properties of the polymer. Isotactic polypropylene is more ordered, less soluble in halocarbons or hydrocarbons, and useful for its higher strength than the more soluble atactic form. Isotactic indices of 90 or higher are favored for commercial polypropylene.
In British Pat. No. 1,577,301 granted to Toyota et al. a process is disclosed for polymerizing olefins with a catalyst component obtained by copulverizing a magnesium halide, Mg alkyl halide, Mg alkoxyhalide, or Mg phenoxyhalide with a carboxylic ester (optionally halogenated) and then mixing the activated product with aliphatic or alicyclic alcohols or a phenol, such as cresol, at room temperature.
Japanese Pat. No. 72/6,408 granted Feb. 23, 1972 to Yamazaki et al. (C.A. 77:49175 g) discloses a polymerization catalyst of titanium trichloride and the reaction products of a trialkylaluminum with adipic acid, benzoic acid, or stearic acid.
U.S. Pat. No. 4,143,223 granted to Toyota et al. discloses a catalytic component obtained by copulverizing a magnesium halide with an organic ester and an active-hydrogen compound, which may be an alcohol or a phenol, and reacting this activated product with a liquid tetravalent titanium halide or alkoxide.
U.S. Pat. No. 4,220,745 granted to Tanaka et al. discloses preparation of a catalytic component by copulverizing magnesium halides and aromatic carboxylic orthoesters with titanium halides.
U.S. Pat. No. 4,082,692 granted to Goldie discloses a fluidized bed of a magnesium compound supporting a titanium catalyst which has been post-treated with an alcohol or phenol.
U.S. Pat. No. 3,642,746 granted to Kashiwa et al. discloses a process for preparing a transition metal catalyst supported on a divalent halide which has been activated by an electron donor and treated by a liquid or gaseous titanium or vanadium compound.
It is an object of this invention to provide a catalytic system for polymerizing olefins, such as propylene, so that de-ashing may be omitted and polymer with high isotactic index prepared. Other objects of the present invention will be apparent to those skilled in the art.